Leorio's power is pretty versatile, I don't think he needs a condition to be strong. He's got long-range attacks, stealth attacks, and according to Ging his Nen ability can be used to attack the body's insides directly. Basically you don't want to get too close to him, but staying at range isn't going to be a great option either. And god help you if he gets the jump on you.
I'd really like to see how a Leorio fight plays out, there's a lot of potential with his moveset.
I'd really like to see how a Leorio fight plays out, there's a lot of potential with his moveset.